1. Field of the Invention
This invention relates to methods and materials for building structures, especially durable wear surfaces such as paved roads, and more particularly to a settable composition based on an aggregate having lightweight ceramic bodies of a disk-like shape, which are mixed with a binder for building roadways and the like.
2. Description of the Prior Art
There are many compositions available for use in constructing roadways. Two main categories are those with a bituminous base and those made with a settable binder such as resin or Portland cement. Both types normally include aggregates such as basalt, flint, granite, limestone, and other ground or chipped rock aggregate. The aggregate particles may be sorted for diameters appropriate for the required use; however, the aggregate is simply broken and/or sorted and no attempt is made to employ any particular shape for the rock pieces.
Some compositions have been developed with the objective of improving the hardness and durability of the materials used in roadways. U.S. Pat. No. 3,776,748 to Richards teaches production of discrete artificial road paving stones by combining a granular aggregate made of silica and clay with Portland cement. The granular aggregate is not fired but is hardened in an autoclave. Lundgren et al. in U.S. Pat. No. 4,050,949 discusses the use of steel disks as an added structural means to reinforce concrete, as opposed to steel wires or the like.
Additionally, aggregates have been used in the production of non-roadway compositions for both decorative and practical reasons. In U.S. Pat. No. 3,078,175 to DeLisle, Terrazo tiles and similar bodies are created by crystalizing a mix of cement and aggregates to form slugs. The slugs are then crushed into random-shaped pieces of the required diameters and compressed to form the tiles.
It is known that powdered or granular aggregates may be added to cementitous products with various results. For example, in the making of concrete bodies, it is known that shale and limestone may be combined with cement and the composition heated until the gases from the limestone cause the mixture to expand. The expanded mixture is then cooled to produce a relatively lighter weight concrete body than would result using inert aggregates. This lightweight cement product is typically formed into blocks. Its surface hardness is not affected by any discrete aggregate pieces included in the mixture.
In related. U.S. Patent Applications Ser. No. 143,587 (U.S. Pat. No. 4,780,433) and Ser. No. 924,891 (U.S. Pat. No. 4,740,486 which are hereby incorporated by reference, I disclosed an inexpensive, lightweight ceramic material to be mixed with cement and which increased the thermal insulation qualities of the cement. The ceramic is added in the form of a crushed aggregate of inexpensive and plentiful clays and organic wastes, mixed and fired to the point of vitrification. The resulting ceramic bodies are left with numerous insulating air pockets at spaces where the organic constituents are burned away during firing. During production the green ceramic, including the organics, is formed into beads or is rolled into sheets or similar forms. The forms are fired and then crushed to create random shapes for aggregate pellets, grains, or similar crushed aggregate.
The present invention uses specially formed aggregate bodies that are not crushed. Preferably the aggregate bodies of the invention are fired beyond vitrification to the point of creating a crystalline glaze on the surface of the beads, whereupon the aggregate pieces are hardened such that with wear of the roadway, or other structure made from the aggregate, the hardened pieces become exposed on the surface, with beneficial results. If the shape of the aggregate is made such that the aggregate bodies are readily layered, especially as a flattened disc, the aggregate is extremely useful in a cement binder composition for roadways.
Comminuted garbage pellets produced from commercial refuse treatment plants are an excellent source of organic material for the aggregate, which organic material is burned out substantially during firing. Therefore, the paving material not only produces a very durable roadway, but consumes undesirable material in the process. During firing of the green ceramic bodies, the organic constituents (i.e., the garbage pellets) also contribute as fuel, reducing the fuel otherwise required, and possibly being adequate for supporting the firing process at certain stages thereof.
Although much prior art is devoted to producing stronger and more durable roadway compositions, the prior art does not lead to manufacturing rock-like ceramic bodies for use with a binder. On the contrary, the conventional wisdom is to break up larger rocks to produce the desired size aggregate bodies. The clay and pelletized garbage, according to the invention, produce a light-weight ceramic aggregate and, when added to a cement binder, produce an economical yet durable roadway composition while at the same time offering an ecologically and economically sound method of using and disposing of organic refuse materials.